1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly, to a paper feeding unit to supply paper to an image forming unit and an image forming apparatus using the paper feeding unit.
2. Description of the Related Art
As shown in FIG. 1, a conventional paper feeding unit of an image forming apparatus comprises a paper feeding cassette 1 to accommodate paper, a pickup roller 2 to pick up the paper in the paper feeding cassette 1, a first feed roller 3 to feed the picked-up paper, a reverse roller 4 to prevent the feeding of a plurality of sheets of paper in cooperation with the first feed roller 3, and second and third feed rollers 5 and 6 which are set up at a predetermined space behind the first feed roller 3.
The first feed roller 3 and the reverse roller 4 are brought into contact with each other to define a predetermined nip therebetween, and they have a rotation direction opposite to each other. Thus, if two pieces of paper are picked up by the pickup roller 2, one of them is fed by the first feed roller 3 in the normal way while the other piece of paper is sent back to the paper feeding cassette 1 by the reverse roller 4.
If an edge of the paper fed by the first feed roller 3 is inserted between the second feed rollers 5 in the paper feeding unit of the conventional image forming apparatus, power to the first feed roller 3 is cut off, and thus the first feed roller 3 becomes idle while the paper is fed by a feeding power of the second feed rollers 5.
Herein, since the reverse roller 4 and the first feed roller 3 are always in contact with each other at a predetermined level of pressure while the reverse roller 4 rotates in the opposite direction with respect to the first feed roller 3, the surfaces of the first feed roller 3 and/or the reverse roller 4 become worn out easily. The abrasion of the surfaces of the rollers is inevitable due to the structure of a conventional paper feeding unit. If the abrasion state is continued, significant noise may be generated. Therefore, the rollers should be replaced with new ones when they reach the end of their lifespan. In the conventional paper feeding unit, the abrasion of the rollers occurs quickly due to the above-described reasons. Therefore, parts must be replaced quite frequently.
Also, the paper feeding unit of the conventional image forming apparatus presses the paper while the first feed roller 3 and the reverse roller 4 are in contact with each other to have a nipping power. Therefore, the second feed rollers 5 should have a feeding power higher than the pressure of the first feed roller 3 and the reverse feed roller 4 when the paper is fed by the second feed rollers 5. Since this requires high-torque operation power, it results in cost increases.